Renforcer, vtr : to reinforce, to strengthen, to increase; to give someone a hand; to heighten, to accentuate.

Ce mur a été renforcé par des contreforts.
This wall has been reinforced with buttresses.

Les pompiers de la ville voisine sont venus nous renforcer.
The firefighters from the neighboring city came to give us a hand.

Le vent renforce toujours le sentiment de froid.
The wind always heightens the feeling of cold.